Heretofore, a fuel cell system including a fuel cell for receiving the supply of a reactant gas (a fuel gas and an oxidizing gas) to generate a power has been suggested and put to practical use. Such a fuel cell system is provided with a fuel supply flow path for allowing the fuel gas supplied from a fuel supply source such as a hydrogen tank to flow to the fuel cell, and the fuel supply flow path is generally provided with a pressure adjustment valve (a regulator) which decreases the supply pressure of the fuel gas from the fuel supply source to a predetermined value. At present, a technology has been suggested in which a mechanical variable pressure adjustment valve (a variable regulator) for changing the supply pressure of the fuel gas in, for example, two stages is provided in the fuel supply flow path to change the supply pressure of the fuel gas in accordance with the operation state of the system.
Moreover, in recent years, a technology has been suggested in which an injector is arranged in the fuel supply flow path of the fuel cell system, and the operation state of this injector is controlled to regulate the supply pressure of the fuel gas in the fuel supply flow path. The injector is an electromagnetic driving type on-off valve in which a valve body can directly be driven with an electromagnetic driving force for a predetermined drive cycle and detached from a valve seat to regulate the state of the gas (a gas flow rate or a gas pressure). A control device drives the valve body of the injector to control a jet timing or a jet time of the fuel gas, whereby the flow rate or the pressure of the fuel gas can be controlled. In recent years, there has been suggested a technology for detecting a trouble (a closure failure such as valve adhering) of an electromagnetic driving type on-off valve such as this injector (e.g., see Japanese Patent Application Laid-Open No. 2005-302563).